1. Field of the Invention
The invention relates to an electrochemical storage cell based on alkali metal and chalcogen with an anodic space and a cathodic space which are separated from each other by an alkali ion-conducting solid electrolyte and are limited at least areawise by a metallic housing, and ceramic structural elements connected with metallic structural elements.
2. Description of the Prior Art
Such electrochemical storage cells are being used increasingly in high-temperature storage batteries which serve as energy sources of electric vehicles.
Rechargeable electrochemical storage cells based on alkali metal and chalcogen, whose reactant spaces are separated from one another by a solid electrolyte, are eminently suitable for the construction of high-temperature storage batteries. The solid electrolytes used in the storage cells, made for example of beta aluminum oxide, have the special feature that the partial conductivity of the movable ions through them is very high, and the partial conductivity of the electrons is smaller by many powers of ten.
The use of such solid electrolytes in the construction of electrochemical storage cells results in practically no self-discharge taking place, as the electro conductivity is negligible, and also because the reaction substances cannot move across the solid electrolyte as neutral particles. One advantage of these storage cells is that no electrochemical side reactions occur during charging. The reason for this is again that only one type of ions can get through the solid electrolyte. The current yield of such a storage cell is therefore approximately 100%.
However, problems still occur with these storage cells in those areas in which ceramic and metallic structural elements are joined together. This is the case in particular in the area of the cell closure, where the insulating ring connected with the solid electrolyte is connected with the housing of the storage cell either directly or via an additional metallic structural element. German DE-OS No. 30 33 438 discloses an electrochemical storage cell in which the ceramic and metallic structural elements are joined together by the use of a thermocompression method. Flat aluminum elements, designed for example as annular disks, are placed between the two structural elements to be connected and serve as adhesion promoters. Since in this thermocompression process the structural elements to be connected are fitted together by aluminum in plastic flow under the action of pressure and heat, one must operate with an aluminum deformation of at least 50%. The structural elements used in the manufacture of the storage cell are preferably made of steel or special steel. The structural elements of the storage cell made of such materials tend to corrode very readily, thereby greatly reducing the longevity of a storage cell. In particular the effectiveness of the storage cell closure is greatly diminished by corroding parts, so that optimum seal of the storage cell from the outside, in particular of its reactant spaces, is no longer assured after a relatively short time.